Fecundity regulation strategy of the blue jack mackerel, Trachurus picturatus (Bowdich, 1825), off Madeira Island (NE Atlantic)

Abstract

This contribution intends to verify the type of fecundity regulation of the blue jack mackerel. For this purpose, the oocyte development process was analysed. A total of 158 ovaries were sampled between January 2009 and April 2010 from purse-seiners operating in the Madeira Island waters, NE Atlantic Ocean. Histological analysis and visual image analysis system were used to study the four main criteria applied for fecundity type determination: (1) presence of a hiatus between pre-vitellogenic and vitellogenic oocytes; (2) number of standing stock of advanced vitellogenic oocytes over the spawning season; (3) mean size of standing stock of advanced vitellogenic oocytes over the spawning season; and (4) the incidence of atresia over the spawning season. The analysis of the oocytes size frequency distribution showed that no distinct hiatus could be observed between pre-vitellogenic and vitellogenic oocytes during the spawning season. Considering the whole spawning period but the last month that was poorly sampled, the number of standing stock of advanced vitellogenic oocytes showed no decrease trend along the spawning season, the mean diameter of cortical alveoli oocytes and of the advanced stock of vitellogenic oocytes did not increase over the spawning season and the relative intensity of atresia was always high throughout this period. These findings suggest the blue jack mackerel displays an indeterminate fecundity.